I. Field of the Invention
The present invention generally relates to devices, systems, and methods for diagnosing and/or treating the heart. In particular, the invention provides methods and systems for sensing heart signals, and especially for localizing and/or treating arrhythmias.
Significant progress has recently been made toward effective treatments of many cardiac arrhythmias. Contraction of a healthy human heart generally propagates through the heart tissue from the sinus node in the right atrium, and eventually the associated ventricles. This normal propagation of contraction forces blood to flow from the atria to the ventricles in a synchronized pumping action. Arrhythmias of the heart often originate at and/or propagate from alternative heart tissues, resulting in rapid irregular or regular contractions of some or all of the heart. Radiofrequency (RF) intracardiac catheter ablation of the alternative ectopic origin, an abnormal conduction pathway, or an abnormal pathway exit site is now used to effectively treat a variety of arrhythmias.
Although quite effective, current catheter ablation for treatment of cardiac arrhythmias has significant disadvantages. A particular challenge in an effective catheter ablation treatment is the time required for proper identification of the treatment site. Careful mapping of the arrhythmia via multiple catheters is generally required to accurately define the treatment site and limit the size of the ablation. Unfortunately, reliably and repeatedly inducing an arrhythmia can be quite difficult, and can result in a lengthy and unpredictable procedure. As an alternative, candidate ablation sites may be tested during normal sinus rhythm by pace mapping. This testing may be quite time-consuming, as it often involves pacing at several sites with an artificial arrhythmia being initiated using a small electrical pulse from a catheter at each site. The candidate sites are often tested sequentially by positioning the intracardiac catheter against a candidate site within (for example) the right ventricle, identifying the engaged tissue location within the ventricle, sensing and/or pacing the heart cycles at the candidate site, repositioning the intracardiac catheter to a new candidate site, and repeating this process until an ectopic origin or an abnormal pathway exit site has been identified.
As fluoroscopy is often used to identify the location of the engaged tissue, this sequential iterative process can result in significant exposure of the patient and treating personnel to potentially harmful radiation. While alternative (and more complex) intracardiac catheter probe structures have been proposed to allow more rapid identification of the ectopic origin(s) or abnormal pathway exit sites of ventricular tachycardias (VTs) and other arrhythmias, the size and cost of these complex structures may limit their acceptability.
To overcome the disadvantages associated with the known, time consuming and/or invasive intracardiac arrhythmia sensing and localization techniques, researchers have been working on alternative arrhythmia localization techniques which rely on body surfacing mapping, often during pacing. Electrocardiograms (ECGs) may be recorded during abnormal atrial or ventricular activity and compared with ECGs taken during pacing at different sites within the heart to help identify the ectopic site, with the ECGs optionally taken using a standard 12-lead ECG system. More detailed information regarding ectopic sites can be obtained by recording heart cycle signals at the body surface using a more comprehensive sensor array (sometimes called body surface ECG mapping or body surface potential mapping). These heart signals, which generally comprise small amplitude variations in electrical potential along the anterior and/or posterior torso, can be manipulated and/or mapped so as to provide an indication of the origin of the arrhythmia within the heart. Much of this work has concentrated on VT. More recent work has begun to investigate the possibility of localizing certain atrial arrhythmias, such as right atrial tachycardia. U.S. Provisional Patent Application No. 60/189,611, filed Mar. 15, 2000, the disclosure of which is hereby incorporated herein by reference, describes exemplary methods and analysis systems for localization and treatment of atrial fibrillation.
While the new body surface mapping techniques appear quite promising, the sensing systems that have been used to-date to measure the heart cycle signals along the body surface have remained less than ideal. The process of preparing patients by affixing known electrode arrays can be time consuming and difficult, even for the highly skilled researchers now developing these techniques. Additionally, many localization procedures will be performed in an electromagnetically xe2x80x9cnoisyxe2x80x9d environment. For example, the imaging equipment (often biplane fluoroscopy), RF power sources, pacing catheters, and therapeutic probes in use in an electrophysiology lab can induce significant noise in the small amplitude voltage measurements on which many of the new arrhythmia localization techniques are based. These imaging, pacing, and treatment systems may also interfere with the ideal array sensing locations. Undesirable interactions between imaging, treatment and body surface mapping electrode arrays may lead to inconvenience and delays at best, and degraded performance and/or increased dangers to the patient at worst. In other words, while the known body surface mapping systems have been adequate for effective research, improved body surface mapping systems and methods would be desirable to allow these new techniques to be effectively, safely, and reliably applied by practicing doctors for treatment of patients.
In light of the above, it would be desirable to provide improved devices, systems, and methods for sensing heart cycle signals for localization of arrhythmias. It would be particularly beneficial if these improvements enhanced the efficiency of mounting an array upon a patient""s torso, as well as increasing the adaptability of the arrays to a variety of patient external anatomies. It would further be beneficial if these improved arrays and body surface mapping methods provided improved safety, reliability, and sensing/localization accuracy, despite the normal variations in physician experience and skill, and without excessive degradation in overall system performance when used in a high electromagnetic noise environment such as an electrophysiology lab. It would further be beneficial to maximize overall system performance without excessive expenditure on individual sensing system components and/or sterilization/reuse procedures. Some or all of these goals are provided by the invention described hereinbelow.
II. Related Art
The following patents and publications may be relevant to the subject matter of the present invention, and their full disclosures are incorporated herein by reference:
U.S. Pat. No. 5,483,968 describes a Method and Apparatus for Analyzing the Electrical Activity of the Heart, and Electrical Clamping Connection Device is described in U.S. Pat. No. 5,733,151. A similar electrode connector is described in PCT Publication No. WO 97/49143. U.S. Pat. No. 6,047,206 which describes Generation of Localized Cardiac Measures, Related Systems, and/or Methods. Similar topics may also be discussed in one or more of U.S. Pat. Nos. 4,751,928; 4,974,598; 5,054,496; 5,634,469; 5,311,873; and 5,724,984.
Arne SippensGroenewegen, et al. described xe2x80x9cBody Surface Mapping During Pacing at Multiple sites in the Human Atrium: P Wave Morphology of Ectopic Right Atrial Activation,xe2x80x9d in Circulation, 98:369-380 (1998). Heidi A. P. Peeters, et al. described related work in an article entitled, xe2x80x9cClinical Application of an Integrated 3-Phase Mapping Technique for Localization of the Site of Origin of Idiopathic Ventricular Tachycardia,xe2x80x9d in Circulation, 99:1300-1311 (1999). Arne SippensGroenewegen, et al. described xe2x80x9cValue of Body Surface Mapping in Localizing the Site of Origin of Ventricular Tachycardia in Patients with Previous Myocardial Infarction,xe2x80x9d in J. Am. Coll. Cardiol. 24:1708-1724 (1994). xe2x80x9cContinuous Localization of Cardiac Activation Sites Using a Database of Multichannel ECG Recordings,xe2x80x9d was described by Mark Potse, et al. in IEEE Trans. Biomed. Eng., 47:682-689 (2000).
Arne SippensGroenewegen, et al. described xe2x80x9cA Radiotransparent Carbon Electrode Array for Body Surface Mapping During Cardiac Catheterizationxe2x80x9d, in the Proceedings of the 9th Annual Conference of IEEE Engineering in Medicine and Biology Society, New York: IEEE Publishing Services, pp. 178-181 (1987). Alexander C. Metting van Rijn, et al. xe2x80x9cPatient Isolation in Multichannel Bioelectric Recordings by Digital Transmission Through a Single Optical Fiber,xe2x80x9d IEEE Trans. Biomed. Eng., 40:302-308 (1993); Alexander C. Metting van Rijn, et al. in xe2x80x9cAmplifiers for Bioelectric Events: A Design with a Minimal Number of Parts,xe2x80x9d Med. and Biol. Eng. and Comput. 32:305-310 (1994); Alexander C. Metting van Rijn, et al. xe2x80x9cHigh-Quality Recording of Bioelectric Events: Part II, Low-Noise, Low-Power Multichannel Amplifier Design,xe2x80x9d Med and Biol. Eng. and Comput. 29:433-440 (1991); and Andre Linnenbank, et al. xe2x80x9cChoosing the Resolution in AD Conversion of Biomedical Signals,xe2x80x9d Building Bridges in Electrocardiology: Proceedings of the CXXIInd Int""l. Congress on Electrocardiology, eds. A. van Oosterom, T. F. Oostendorp, G. J. H. Uijen, Nijmegen, The Netherlands: University Press Nijmegen, pp. 198-199 (1995), may also be relevant.
The present invention provides improved systems, devices, and methods for sensing and/or diagnosing arrhythmias of a heart. The improved systems and methods often sense heart signals through a torso surface of a patient. These improved systems generally facilitate mounting of an array of sensors upon the patient""s torso by supporting the sensor arrays on one or more panels. In the exemplary embodiment, four separate panels are adapted for engaging the torso surface, with the four panels supporting most or all of the sensors necessary for localizing an arrhythmia within a chamber of a heart of a patient. The panels may have integrated components for use with other electrophysiology lab equipment such as cardiac imagers, defibrillation power sources, therapeutic probes, standard 12-lead electrocardiogram (ECG) systems, and the like. In the exemplary embodiment, an arrhythmia sensing system is adapted for use in the high-noise environment of an electrophysiology lab by including a series of powered circuits distributed among the electrodes of the array. The powered circuits are supported by the panel structure for local amplification, defibrillation protection (often using an electrical energy limiter such as a diode), and the like. Still further functions may be performed locally (in some embodiments) such as conversion of electrical analog signals to digital data and/or optical signals, and the like, or at least some of these functions may instead be performed by a separate transmission signal processing structure between the panels and an arrhythmia analyzer, or even by the analyzer itself. A separate low-noise (and often low-cost) arrhythmia sensing system may be useful for initially recording an abnormal irregular or regular heartbeat outside the electrophysiology lab. These improvements generally enhance the ease of arrhythmia localization, the localization accuracy, and the cost of diagnosis, allowing these highly advantageous body surface mapping techniques to move from academic and research studies to practical tools for treatment of patients.
In a first aspect, the invention provides a sensing system for diagnosing and/or treating a heart of a patient. The patient has a torso surface. The sensing system comprises an array of sensors for sensing heart cycle signals. Four sensor support panels have panel surfaces adapted for engaging the torso surface. The four panels support a majority of the sensors of the array in communication with the torso surface when the panels engage the torso surface.
Preferably, the array will define at least forty (40) sensing locations, with each panel supporting at least 5 sensors, and more preferably at least 7 sensors. The panels can be adapted for alignment with the torso surface, with the sensors of each panel being distributed both along a superior-inferior length and along a lateral width of the panel. The four panels can have leads extending from the sensors for transmitting sensor signals to the analyzer, with the leads preferably extending from each of the panels toward a common lateral side of the patient so as to enhance access to the patient. The leads may optionally comprise a flexible lead material which is selectively deposited or etched along a flexible panel substrate. Ideally, the panels are single-use, disposable structures to avoid the cost and dangers of reuse.
While it is possible to select an appropriate array from a large number of single-panel structures so as to accommodate a particular patient""s external anatomy, or to include elastic or other variable size support structures so as to adapt to a wide range of external anatomies, the present application will preferably make use of a limited number (typically two to eight, and ideally four) independent panels. These sets of panels may be selected from a limited number of set sizes, typically from 2 to 10 different sizes, to accommodate different size patients, and ideally from 3 different sizes to accommodate small, medium, and large patients, with the individual panel sizes varying between the different size panel sets. Each panel can comprise a flexible, inelastic substrate, and/or each panel may be mounted independently on the torso surface, typically using a sticky or adhesive torso/panel interface material. This interface may also provide selective electrical coupling of the electrodes of the array to target sensing locations of the torso surface. By independently positioning the panels, a relatively small number of panel sets may be sufficient to accommodate a wide range of patients.
In the exemplary embodiment, severable cross-members of at least some of the panels allow the panel configuration to be modified to accommodate differing external anatomies, (for example, to accommodate breasts and the like). The four panels will ideally each be associated with a quadrant of the torso, for example, providing a right front torso quadrant panel, a left front quadrant panel, a right rear quadrant panel, and a left rear quadrant panel. Still further, alternative structures may be provided to enhance the comfort of many embodiments of the present sensing system, particularly for embodiments intended for extended use. Optionally, such sensing systems may be adapted to provide ambulatory recording for use over a plurality of hours, often for 24 hours or more, and in some cases for 48 hours or more. Such ambulatory recording systems will often comprise a portable power supply (such as a battery) and a portable recording device (such as a non-volatile memory, a magnetic and/or optical recording media and associated drive, or the like).
It will often be advantageous to provide means for accessing the heart cycle signals as measured from the six or twelve standard ECG sensing locations. Such access allows the sensing system to remain in place when using a variety of other electrocardiography systems. The means for accessing may comprise one or more standard or proprietary lead connectors for transmitting sensor signals also used by the arrhythmia analyzer. Alternatively, connectors at the appropriately positioned sensors of the array may be provided, or simple openings in the panel or panels at some or all of the twelve standard lead positions may be included.
In another aspect, the invention provides an apparatus for use with a cardiac stimulation power source and an arrhythmia analyzer for localizing an arrhythmia within a chamber of a heart of a patient. The patient has a torso surface, and the apparatus comprises at least one panel adapted for engaging the torso surface. A cardiac stimulation electrode is mounted to the at least one panel for transmitting energy from the stimulation power source to stimulate the heart. An array of sensors are mounted to the at least one panel. The sensor array transmits sensor signals to the analyzer for localizing the arrhythmia.
In many embodiments, a pair of stimulation or defibrillation electrodes will be mounted to the at least one panel so as to position the heart of the patient between the stimulation electrodes. Often times, one or more sensors of the array will be disposed within a perimeter of the stimulation electrode. Such sensors may be electrically isolated from the stimulation electrode. An imaging window may extend through the panel for imaging of the heart, with at least a portion of the stimulation electrode being disposed within the imaging window. So as to avoid degrading image quality, the portion of the electrode within the imaging window may be adapted to allow imaging therethrough.
In another aspect, the invention provides an apparatus for use with an arrhythmia analyzer and one or more remote imagers when monitoring a patient. The patient has a heart within a torso surface. The apparatus comprises at least one panel having a surface suitable for engaging at least a portion of the torso surface. An array of cardiac signal sensors are mounted to the at least one panel. The sensor array generates signals in response to heart cycle signals for transmission to the arrhythmia analyzer. An imaging window extends through the at least one panel for imaging the heart.
In the exemplary embodiment, a plurality of imaging windows extend through the at least one panel for three-dimensional imaging of the heart, typically using bi-plane fluoroscopy. One or more sensors of the array may be disposed within the imaging window, with such sensors typically being more transparent to the imager than at least some of the sensors disposed beyond the imaging window. For example, sensors within the imaging window may comprise radiotransparent carbon electrodes, while one or more of the sensors disposed beyond the window may comprise a silver/silver chloride electrode. Where powered circuits are distributed among the sensors of the array to avoid noise, the powered circuits will often be disposed outside the imaging window. Similarly, electrical leads within the imaging window may have an enhanced radiotransparency as compared to electrical leads disposed outside the window. For example, thicknesses of leads within the imaging window may be reduced, lead materials may be changed, or the like. Once again, one or more cardiac stimulation electrodes may be mounted to the at least one panel.
In yet another aspect, the invention provides an arrhythmia localization system for diagnosing an arrhythmia of a heart within a torso surface of a patient. The arrhythmia localization system comprises a noisy-environment sensor system, including a substrate for mounting upon the torso surface, an array of sensors mounted to the substrate, and a plurality of powered circuits distributed among the sensor for transmitting sensor signals. An arrhythmia analyzer is coupleable to the powered circuits for identifying a candidate arrhythmia site within a chamber of the heart of the patient.
Optionally, a separate low-noise environment sensor system may also be provided, with the low-noise system including a substrate for mounting upon the torso surface and an array of sensors mounted to the substrate for recording signals during an abnormal irregular or regular heart beat. The arrhythmia analyzer may identify the candidate arrhythmia site in response to the heart cycle signals sensed by the noisy environment sensor system, and in response to the recorded abnormal heart signals.
In a method aspect, the invention provides an arrhythmia localization method comprising engaging at least one panel against a torso of a patient body. Heart cycle signals are sensed with an array of signals supported by at least one panel. An arrhythmia is localized within a chamber of the heart using the sensed heart cycle signals. Typically, the sensed heart cycle signals are processed with a plurality of powered circuits supported by the at least one panel, the powered circuits distributed among the sensors to inhibit noise.